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| [5.0rc2] OpenGL/Deferred drawing CPU use |
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Bullet
Member #12,431
December 2010
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I might be miss using deferred drawing here but when using it with OpenGL the cpu usage goes to about 50%, without deferred drawing it only uses a few percent. Works fine with directX. 1#include <allegro5/allegro.h>
2
3
4int main()
5{
6 if(!al_init())
7 return 1;
8
9 if(!al_install_keyboard())
10 return 1;
11
12
13 al_set_new_display_option(ALLEGRO_VSYNC, 1, ALLEGRO_SUGGEST);
14 al_set_new_display_flags(ALLEGRO_OPENGL);
15
16 ALLEGRO_DISPLAY* display = al_create_display(200, 200);
17
18 if(!display)
19 return 1;
20
21 ALLEGRO_EVENT_QUEUE* queue = al_create_event_queue();
22
23 if(!queue)
24 {
25 al_destroy_display(display);
26 return 1;
27 }
28
29 al_register_event_source(queue, al_get_keyboard_event_source());
30 al_register_event_source(queue, al_get_display_event_source(display));
31
32 ALLEGRO_BITMAP* image = al_create_bitmap(20, 20);
33
34 if(!image)
35 {
36 al_destroy_event_queue(queue);
37 al_destroy_display(display);
38 return 1;
39 }
40
41 al_set_target_bitmap(image);
42 al_clear_to_color(al_map_rgb(255, 255, 255));
43 al_set_target_bitmap(al_get_backbuffer(display));
44
45 bool IsRunning = true;
46 while(IsRunning)
47 {
48 ALLEGRO_EVENT Event;
49
50 while(al_get_next_event(queue, &Event))
51 {
52 if(Event.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
53 {
54 IsRunning = false;
55 }
56 else if(Event.type == ALLEGRO_EVENT_KEY_UP &&
57 Event.keyboard.keycode == ALLEGRO_KEY_ESCAPE)
58 {
59 IsRunning = false;
60 }
61 }
62
63 al_clear_to_color(al_map_rgb(0, 0, 0));
64
65 al_hold_bitmap_drawing(true);
66 for(unsigned i = 0; i < 9; i++)
67 {
68 float X = i * 22.0f;
69
70 for(unsigned j = 0; j < 9; j++)
71 {
72 float Y = j * 22.0f;
73 al_draw_bitmap(image, X, Y, 0);
74 }
75 }
76 al_hold_bitmap_drawing(false);
77
78 al_flip_display();
79 }
80
81 al_destroy_bitmap(image);
82 al_destroy_event_queue(queue);
83 al_destroy_display(display);
84
85 return 0;
86}
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Elias
Member #358
May 2000
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I can't seem to reproduce here. This is oprofile output of your example with held drawing: 13268 60.7120 libnvidia-glcore.so.260.19.06 /usr/lib/nvidia-current/libnvidia-glcore.so.260.19.06 1082 4.9510 libGL.so.260.19.06 /usr/lib/nvidia-current/libGL.so.260.19.06 1054 4.8229 liballegro-debug.so.5.1.0 draw_quad 575 2.6311 ld-2.12.1.so __tls_get_addr 437 1.9996 liballegro-debug.so.5.1.0 tls_get 345 1.5787 liballegro-debug.so.5.1.0 _draw_tinted_rotated_scaled_bitmap_region 300 1.3727 liballegro-debug.so.5.1.0 al_compose_transform 259 1.1851 liballegro-debug.so.5.1.0 al_identity_transform 250 1.1440 libc-2.12.1.so memcpy 230 1.0524 liballegro-debug.so.5.1.0 al_rotate_transform 230 1.0524 liballegro-debug.so.5.1.0 al_transform_coordinates This is without: 9394 59.3618 libnvidia-glcore.so.260.19.06 /usr/lib/nvidia-current/libnvidia-glcore.so.260.19.06 749 4.7330 libGL.so.260.19.06 /usr/lib/nvidia-current/libGL.so.260.19.06 458 2.8942 liballegro-debug.so.5.1.0 draw_quad 454 2.8689 libc-2.12.1.so fgetc 405 2.5592 libX11.so.6.3.0 /usr/lib/libX11.so.6.3.0 229 1.4471 ld-2.12.1.so __tls_get_addr 209 1.3207 libc-2.12.1.so __GI___strcmp_ssse3 169 1.0679 liballegro-debug.so.5.1.0 _draw_tinted_rotated_scaled_bitmap_region 160 1.0111 libc-2.12.1.so memcpy One difference you can see is that with held drawing, we do transformations in software, so for each bitmap there's calls to the transformations functions - so they show up at the top. Without held drawing transformations are done on the GPU so they don't show up. However I can't see this causing 50% CPU... in my case it makes no difference on the end result. It also would show up with D3D. It would be interesting seeing profiling output but I don't think you can get that in Windows. But maybe there's something in allegro.log which can give a hint, so if you can try compiling it with the debug version of Allegro and attach the allegro.log file it might help find the problem. -- |
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Bullet
Member #12,431
December 2010
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Log attached. |
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Elias
Member #358
May 2000
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Hm, nothing out of the ordinary. How many cores do you have? I assume 50% CPU means half of them are spin-locking. Maybe some threading issue with our wgl implementation. Not sure how to look into it without being able to reproduce. Can someone else reproduce this? -- |
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Bullet
Member #12,431
December 2010
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Yes, the cpu has two cores. EDIT: Neither core is completely saturated one is at about 75% and the other at about 25%. |
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Elias
Member #358
May 2000
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That could just mean that the kernel is switching load between the cores. I wonder if it has something to do with tls_get (which shows up as 2% in my profiling results with held drawing) - I don't see why the OpenGL and D3D drivers would call it different amounts of time though. Let's wait if someone else can reproduce it. I'll also try it on my netbook. -- |
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